Overview

NEA is the global leader in non-pyrotechnic Hold Down & Release Mechanisms (HDRM) for the spacecraft market. Hold Down & Release Mechanisms, also sometimes referred to as Separation Nut Release Mechanisms, are offered in a range of sizes with load capacities up to a 500 kN (112,000 pounds force).

Principle of Operation

The NEA HDRM is an electrically initiated, one-shot release mechanism that has the ability to carry a very high tensile preload until commanded to release. The preload is applied through a release rod held in place by two separable spool halves which are in turn held together by tight winding of restraining wire. The restraint wire is held in place by redundant electrical fuse wires; actuation of either circuit allows release, assuring maximum reliability. When sufficient electrical current is applied, the restraint wire unwinds allowing the spool halves to separate releasing the release rod and the associated preload.

The actuation is simple and reliable and forms the basis of actuation for many of NEA’s other products including Pin Pullers, Battery Cell Bypass Switches, and Non-Pyrotechnic Valves.

Technical Advantages

NEA release device technology provides significant advantages.

Low Shock

There are three sources of shock with traditional pyrotechnic release devices; those include the pyrotechnic initiator and the resulting transfer of kinetic energy within the mechanism. The NEA approach eliminates both of these sources of shock. There is no pyrotechnic initiator required so there is no initial shock and the restraint wire release mechanism is also not a significant contributor to shock.

A third source of shock is the energy stored in the release rod itself as well as any of the other components that are in the preload path. The nature of NEA device's gentle release of preload allows this stored energy to be dissipated over the release event minimizing the stored energy contribution to shock as well.

Fast Acting

With respect to shock, the action of NEA devices is quite gentle yet the release event itself is still very fast. Since the bridge wire is extremely small the release event can be triggered in milliseconds. This capability allows multiple NEA devices to be used in parallel where simultaneous release is required, such as large solar array panels and spacecraft stage separations.

Reliable

With simplicity comes reliability. The basic design of the NEA HDRM is very simple with a minimum of moving components. The devices are robust and not sensitive to extreme environments or contaminants. High reliability is supported both analytically and by an extensive history of successful operation in mission critical applications.

Light Weight

Temperature Insensitive

The simplicity of the NEA release device mechanism is an asset not just for reliability but also with respect to temperature sensitivity. NEA HDRMs are insensitive to extreme temperatures. Specific NEA HDRMs have been qualified for operation at temperatures as low as 25K. The extreme low mass of the bridge wire results in actuation performance that insenstive to initial conditions.

Low Risk

NEA HDRMs have an extensive history of use on a broad variety of spaceflight applications and are currently the baseline release device of choice on most major spacecraft buses. This history of reliability and mission success makes the NEA HDRM our customers' low risk option.

Compatible

NEA HDRM devices have been designed to work with existing pyro firing circuits. The flexibility of the design however also allows operation with lower firing current if required.

Custom Configurations

In addition to our line of standard HDRM devices NEA can provide custom configurations that include; modifications to the mechanical interface, modified housing designs, changes to lead wires, revisions to load capability, additional connector housings, and release rod capture assemblies. NEA can also provide HDRM devices as part of a next higher assembly either built to our customer's prints or designed at NEA to our customer's specifications. Our HDRMs can also be integrated into our electromechanical gimbal actuators as part of a launch restraint system for antennas.

Many of our current customers rely on NEA's in-house engineering expertise to integrate our market leading split-spool HDRM technology into custom assemblies to improve their competitive edge.

Typical HDRM Actuation Curve

A typical HDRM actuation curve showing the actuation time as a function of the actuation current is presented below. Please contact our applications engineers for specific curves for each product.

Notes:1Shock is preload dependent, contact applications engineering for shock at other preloads.2Actuation can be achieved using a range of current, the value in the table is a nominal value applied for 25 ms.3Release time is a function of actuation current, contact applications engineering for more specific actuation time as a function of current curves.4The values presented for qualification temperature range are not a measure of the limits of the device.5Mass does not include harnessing and lead wires.6CAD Model is provided for convenience and reference only.